Since the NOL is for 2016, you follow 2016 rules for the NOL. It may be carried back, and even though 2014 and 2015 are "closed" years, they are re-opened for a claim of an NOL.
A Net Operating Loss is a very complicated subject, to be sure, and obtaining a professional is not a bad idea, especially since after tomorrow TurboTax 2015 will no longer be available (and 2014 already is not available).
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